1. Field
The present disclosure relates to a cooling structure of an internal combustion.
2. Description of the Related Art
Typically, in a multi-cylinder engine, a plurality of intake ports and exhaust ports are formed inside a cylinder head, and an intake manifold that distributes the intake air and an exhaust manifold that merges the exhaust air are joined to an intake side lateral surface and an exhaust side lateral surface, respectively, of the cylinder head. In recent years, there are multi-cylinder engines in which the exhaust collection portion that merges the exhaust air is formed inside the cylinder head such that a single exhaust outlet is formed in the exhaust side lateral surface of the cylinder head and a single exhaust pipe is joined to the cylinder head.
A multi-cylinder engine in which the exhaust collection portion is formed inside the cylinder head does not need to be provided with a separate exhaust manifold; accordingly, the engine as a whole can be reduced in size, the amount of heat discharge of the exhaust gas can be suppressed, and the temperature of the exhaust gas purifier at the time of warm up can be increased promptly, activating the catalyst. Furthermore, since the distance from the combustion chambers to the exit of the exhaust collection portion can be made short, when providing a supercharger (turbocharger) that uses exhaust gas, the response of the supercharger can be improved.
On the other hand, in a cylinder head in which the exhaust collection portion is formed therein, since the exposed area of the exhaust ports and the exhaust collection portion is large, the area in the vicinity of the exhaust collection portion needs to be cooled in order to prevent excessive increase in temperature. In a known cooling structure of an internal combustion engine that also cools the vicinity of an exhaust collection portion formed inside a cylinder head, in order to uniformly cool vicinities of combustion chambers and an exhaust manifold (the collection portion), water flows that flow in a direction orthogonal to a cylinder row direction are formed, and connection portions for continuously supplying a coolant to a three piece water jacket stacked in the cylinder axis direction are provided (see Japanese Unexamined Patent Application Publication No. 2012-189075).